NATURAL PHILOSOPHY. 121 



has completed this classification, by adding to his horizontal chromatic 

 circle a series of vertical circles, containing all the intermediate 

 nuances. By this, every color, simple or binary, gives twenty tones ; 

 the seventy-two colors of the chromatic table above indicated, give, 

 multiplied by twenty, ...... 1440 tones. 



Each simple, or binary color, giving, besides, nine gam- 

 uts, each of which has twenty tones, we have . . 12,960 " 

 Add the differences [degradations'] from black to white, 



which give twenty-one tones, . . . . . 21 " 



We have a total of tones, ..... 14,421 

 By the aid of this table any one can designate in future any and all 

 colors imaginable, whether applicable to printing, painting, or any 

 other object ; in chemistry, the colors of all substances, precipitates, 

 &c., can be defined with a precision which until now has been impossi- 

 ble ; and in natural history the colors of living animals, their changes 

 at different periods of their life, and the colors of their different varie- 

 ties, can be ascertained with the last precision. For example, M. 

 Chevreuil states that in the violet there are twenty-eight colors, and in 

 the dahlia forty-two. 



POLARIZATION OF THE CHEMICAL RAYS EXISTING IN SOLAR LIGHT. 



IT is well known that physicists have found in the solar spectrum, 

 produced by means of a good prism, three orders of relations, which 

 are in part superposed, the calorific, the colorific or luminous, and the 

 chemical. The rays of the two first orders are susceptible of polariza- 

 tion, and consequently of extinction. The chemical rays, however, have 

 not until quite recently been examined in this respect. Professor E. 

 Wartman, of Geneva, Switzerland, has, during the past year, shown 

 that, like the rays of heat and light, the chemical ray is susceptible 

 of polarization and of complete extinguishment. The conditions under 

 which the experiment was effected were similar to those ordinarily 

 made use of in polarization, an exquisitely sensitive daguerreotype 



being the test. 



ARAGO ON POLARIZED LIGHT. 



A PAPER was recently read before the French Academy, by M. Arago, 

 relative to his further researches on light.* The following is an ab- 

 stract : " Up to the present time no means have been furnished of 

 measuring the quantities of polarized light contained in a ray reflected 

 by a surface which does not completely polarize the light. M. Arago, 

 by employing a pile of glass plates, placed so as to incline suitably on 

 the track of a reflected ray, so as to obtain neutral light, has found that 

 at an equal number of degrees above and below the angle of maximum 

 polarization, the proportion of polarized light contained in a ray was 

 the same ; a fact which has enabled him to determine the angle of the 

 maximum polarization of certain metals, such, for instance, as steel and 



* See Annual of Scientific Discovery, 1851, pp. 137, 139, 140. 



